The superdistribution is a scheme which smoothly circulates a content on a network.
In the superdistribution, a content provider delivers an encrypted content encrypted by any method to a user. The content provider or a key manager provides the user with a decryption key which decrypts the encrypted content in addition to the encrypted content. The user is allowed to use the content by purchasing the decryption key.
Usually, in the superdistribution, the content is encrypted and protected. The encrypted content is available at no charge, and can be obtained by any route.
The encrypted content is decrypted in specific software by using the decryption key, and the content is thereby utilized by the user.
The superdistribution assures copyright protection of the content and convenience of the user at the same time, and facilitates circulation of the content. In the superdistribution, the following effects such as those described in (1) to (4) can be obtained.
(1) The electronic circulation enables the content to be rapidly distributed, and dramatically increases circulation of the content as compared with a current situation.
(2) Illegal copying can be avoided, and a right for a content right holder such as a copyright holder of the content can be protected. Since the content is encrypted, the content cannot be utilized unless the decryption key is obtained even if illegal copying is carried out.(3) A charge for utilizing the content can be reduced. That is, a content utilization fee does not have to be set with an added coverage amount for losses due to illegal copying, a cost required for circulation is also reduced, and hence a utilization fee of the content itself is decreased.(4) A charge according to a number can be effected, contents can be freely used.
Patent Reference 1 (Jpn. Pat. Appln. KOKAI Publication No. 2002-288449) discloses a technique which downloads a content and then again downloads the content.
In the invention described in Patent Reference 1, a server device and/or a client device holds a purchase record of the once downloaded content. The client device requests downloading the content which exists in the purchase record while making reference to the purchase record, and again downloads the content. The server device refers to the purchase record, and checks the purchase record, and performs the redownload with a counter value which is appropriate for the client side, depending on the redownload request.
Besides, Patent Reference 2 (Jpn. Pat. Appln. KOKAI Publication No. 2002-63500) and Patent Reference 3 (Jpn. Pat. Appln. KOKAI Publication No. 2002-245268) disclose inventions concerning reacquisition of a content.
Further, Patent Reference 4 (Jpn. Pat. Appln. KOKAI Publication No. 2001-184314) discloses a storage device for a purchased content.
In general, a user in the superdistribution stores a content in a user terminal such as a personal computer, or stores the content in a recording medium such as a flexible disk.
However, there are many particulars which can be factors of loss of the content, e.g., defects in a hard disk, problems in an operating system (which will be referred to as an “OS” hereinafter), human errors, theft or loss of the user terminal or the recording medium or natural disasters such as earthquakes or fires, and it is difficult to assuredly store the content.
Therefore, in the superdistribution, when the user loses the content, it is desired that efficient reacquisition of the content is possible without having a lot of labor of the user.
In case of reacquiring the content, there is generally utilized a method by which the user redownloads the content from a site where he/she has downloaded the same before or the user uses any search engine to find and redownload the lost content.
However, it is difficult to efficiently reacquire the content by this method.
For example, even if the user again accesses the site from which he/she has downloaded the content before, it is not guaranteed that he/she can rapidly find and redownload the content. That is because provision of the content has already come to an end, for example.
Furthermore, in cases where the search engine is used, a searching operation itself is a burden to the user, it takes time for the user to immediately find the lost content due to the influence of search noises or the like, and reacquisition of the content is difficult in some cases.
Patent References 1 to 4 mentioned above describe reacquisition and storage of the content. However, these references do not describe a scheme in which the user edits a once-acquired content and saves and reacquires the edited content in the superdistribution.
For example, in regard to the content such as a newspaper, a magazine (a weekly magazine) or the like, although the user does not have to save the entire content after reading, he/she may want to pick up and use an article in the content in some cases. In such a case, if the entire content is saved in a server, a capacity of the server becomes enormous, which may be a factor of occurrence of an error in the server.
Moreover, saving the entire content and again performing an editing operation such as a selecting a part of the content may be possibly an infringement of a right, e.g., a copyright concerning the content. Therefore, there is required a scheme which avoids an infringement to the right concerning content and enables reacquisition of the edited content.
Although the content provided to the user terminal is stored in the server or the like in Patent References 1 to 4, the same content is recorded with respect to each user even if the same content is acquired by a plurality of users. Therefore, there may be a case in which overlap of contents recorded in the server occurs and a capacity of the server becomes enormous, which leads to generation of an error in the server. In particular, this problem becomes more serious as the number of users and the number of contents to be distributed to users are increased.
In view of the above-described problems, it is an object of the present invention to provide a content management system, and a recording medium and method which reduce a number and capacity of contents to be stored, easily and rapidly reacquire content and make storage of the contents more efficient.